Infants who are breastfed have lower arsenic levels than those who are fed formula, according to a U.S. study released Monday that suggested another breastfeeding benefit.

The study, published online in the U.S. journal Environmental Health Perspectives, measured arsenic in home tap water, urine from 72 six-week-old infants and breast milk from nine women in the U.S. state of New Hampshire.

Urinary arsenic concentrations were generally low but 7.5 times higher for infants fed exclusively with formula than infants fed exclusively with breast milk, it found.

"This study's results highlight that breastfeeding can reduce arsenic exposure even at the relatively low levels of arsenic typically experienced in the United States," lead author Kathryn Cottingham, professor of Dartmouth College, said in a statement. " This is an important public health benefit of breastfeeding."

Cottingham noted that the findings also apply to newborns in other countries or regions.

"Breast milk is very low in arsenic, should hold worldwide," she wrote in an email to Xinhua. "In fact, low arsenic in breast milk has already been reported from a number of countries where drinking water arsenic can be very high, including India, Bangladesh, and Chile."

Specially, infants with the highest exposures in this study were exposed to more arsenic because of their drinking water, not the formula powder, Cottingham said.

"So it is the water that should be of most concern in limiting total exposures," she said, urging families with private wells in rural areas to have their tap water tested for arsenic.

Arsenic occurs naturally in bedrock and is a common global contaminant of well water. It causes cancers and other diseases, and early-life exposure has been associated with increased fetal mortality, decreased birth weight and diminished cognitive function.